Abstract (EN):
Drying kinetics of biofilms from chestnut starch and hybrid carrageenan were experimentally determined and modelled. The biofilms were obtained by mixing the respective solutions (4.0% w/w) of both substances in the proportion 80/20 of chestnut starch/hybrid carrageenan. Glycerol (at 5.0% w/w) was added to some biofilms. Biofilms were prepared using a casting method. Drying kinetics were performed at 30, 40, and 50 degrees C for forced air convection (1.8 +/- 0.1 m/s) and 30 and 50 degrees C for natural convection. Constant drying rate period, above critical moisture content (5.4 and 4.2 kg water/kg d.b. without and with glycerol, respectively) allowed the evaluation of the heat transfer coefficients. The water diffusion coefficients were determined in the falling rate period assuming a semi-infinite slab with variable thickness. Water sorption isotherms of biofilms at 25 degrees C were determined and fitted with the GAB model. Mechanical properties of different biofilms showed no significant differences for Young's modulus values (44.0 +/- 4.6 MPa). Nevertheless, films prepared at 30 degrees C under natural drying showed the lowest values of tensile strength and elongation (32.2 +/- 4.9MPa and 0.85 +/- 0.11%).
Idioma:
Inglês
Tipo (Avaliação Docente):
Científica
Nº de páginas:
8